نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
The present study investigates the oxidation behavior of GTD-111 nickel base superalloy at 1000 °C in air. To this aim, several techniques including thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), grazing incidence X-ray diffraction (GI-XRD) and glow discharge optical emission spectroscopy (GDOES) were employed. The oxidation kinetics of this superalloy alters from linear to parabolic after 10 h exposure which is accompanied by the formation of a uniform surface oxide layer. Based on the cross-sectional analysis of FE-SEM and GDOES, Ti can most probably be considered as the first species which enters the reaction front when oxidation begins. However, as a result of its oxidation, Ti is depleted just beneath the oxide scale, and conditions changes in favor of the formation of other oxides, namely, Cr2O3. Subsequently, due to the internal diffusion of O2- species, Al is internally oxidized, and islands of Al2O3 form underneath the oxide layer. After 100 h of oxidation, the chemical composition of the oxide film consists of an Al-rich inner region, a Ti-rich outer region, and a Cr-rich intermediate layer. GI-XRD results also confirmed the formation of mentioned oxide phases. No indication of oxide spallation and formation of nickel oxides were observed even after 100 h of oxidation.
کلیدواژهها English